my 2001 astra estate is misfiring, been into the garage for a diagnostic and they have replaced the crank sensor but still misfiring once warmed up , I changed the plugs and air filter before it went to the garage . some people have suggested an engine oil flush but I have read this can damage the engine . had the car 3 years and do about 10000 k a year , I change the oil and filter every year and its due to be redone was considering an engine oil flush , but worried about damaging the engine , also gonna change the leads . any advice much appreciated .
If you ride the car regularly and change the oil regularly, there should be no reason for an engine flush.
Only if you used cheap, mineral oil, there could be some gunk build up inside the engine.
If done properly engine oil flush should not damage the engine.
Most things done in a hurry need to be done again - patiently.
Might be the EGR valve but also give the throttle bodies a clean. Give Vauxhall Owners Network a try, they've been v useful keeping my Astra CDX estate on the road.
S
Someone sent me a postcard picture of the earth. On the back it said, "Wish you were here."
Steven Wright
(30-06-13, 10:51 PM)CRH link Wrote: coil pack!!....my zafira did same now bang on 
Plus one for the coil pack and/or plugs.
Oil won't cause it to mis-fire and in all my years have never used any oil flush - no need to if its changed regularly.
Those are my principles...if you don't like them I have others.
:agree
Oil wont cause it and neither will the EGR valve. Its more likely to be a coil pack breaking down (or leads/distributor depending on how old the car is) when it gets warm.
Another ex-Fazer rider that is a foccer again
I agree coilpack.. or possibly a dodgy earth point. My Mrs car had "missfire on multiple cylinders" as a fault and found on wiring diagram the earth point for the coils was on the chassis and not on the engine itself. odd I know but wire wool and a bit of copperslip fixed it.
On the engine flush topic I have a mate who works in VW tech dept and they advise against engine flush these days.. With modern engine oil being so good it is less likley to sludge up and the chemicals in engine flush do more harm than good.
Lord,
Grant me the WD-40 to move those things that are stuck, the Duck tape to fasten those things that are loose, And the wisdom to know the difference.
Amen
The mechanic who carried out the diagnostic , has said to wait a few days as sometimes it takes a few days for the computer to recognise the new part , is this correct?. if the fault persists he wants the car back to check it again , my nephew who is a mechanic also said coil pack or leads depending on car .
In my experience I plug my code reader in. get fault code and google it.. I have always in the past had a good idea of what the fault is due to the code and fixed many things on various cars in this manner..
My point is the ECU should not need to "learn" it has a new part but you reset the fault code and then see if it comes back.
The way vauxhall cars work is that even if it logs the fault once it will then show this for the next 8 engine starts. If no fault in that time it will clear the light but the fault code remains in the cars ecu. (I own a vectra and do all my own work so stuff I have learnt)
Does it have an engine management light on?
If your mechanic has an OBD code reader ask for the code and look it up.
http://www.troublecodes.net/OBD2/Pcodes.shtml
Lord,
Grant me the WD-40 to move those things that are stuck, the Duck tape to fasten those things that are loose, And the wisdom to know the difference.
Amen
With misfiring and rough running you might need a fuel system flush/clean. There is a system that has been on the market for a few years that plugs into the fuel injection. You disable the fuel pump and run the car on the chemical flushing system, it cleans all the injectors with one chemical then cleans out the carbon build up from the combustion chamber through to the back of the exhaust with another. It takes about an hour and costs about £75 to £100 depending on engine size/number of cylinders.
I have an 8 year old 110,000 mile Nissan and had mine done at the Nissan dealer (here in Saudi) with a Bosch System, it made the engine run smoother and made a measurable improvement in the emissions.
The engine management light came back on this evening , so gonna get the mechanic to check it again , I did consider a fuel issue but as the misfiring only happens when the car is warmed up , I have assumed that if it was fuel issue it would also misfire when its cold?
